lesson 1: i learned that different surfaces have different amounts of friction. the fine sandpaper has the most friction.

lesson 2: i learned that with more weight comes more friction. like if you pull 2 blocks, it has more friction than with just 1.

lesson 3: i learned that different sides of the block have different amounts of friction, but its not much of a difference.

we measured sliding friction by using spring scales in class. friction can be measured when it pulls back on the object you are pulling. so when you pull it, you can measure the resistance with a spring scale, and that is
friction and that is how you can measure friction with a spring scale.

we learned that controlled variables are important. plus also here are some examples.
1:distance pulled
2:slope
3:surface type
4:speed
5:block type
those are things that are controlled variables, which means they stay the same.